Approximately 65% of service members seriously injured in Iraq and Afghanistan sustain injuries to their extremities. Many of these individuals experience muscle tissue loss and/or nerve injury, resulting in the loss of limb function or substantial reduction thereof. Many devices used for the treatment of lower-extremity pathology, e.g., knee orthoses, are passive devices. Increasingly, robotic technology is employed in the treatment of individuals suffering from limb pathology, either for the advancement of therapy tools or as permanent assistive devices. Upper-extremity robotic devices provide assistance and therapy for improved reaching and manipulation and, lower-extremity robotic devices have been developed for the enhancement of locomotor function.
Although decades of research has been conducted in the area of active permanent assistive devices for the treatment of lower-extremity pathology, these devices are not designed to produce a biomimetic response, generally described in terms of joint torque, joint angle, and other related parameters as observed in a human not having substantial muscle tissue injury and not using any device to assist in ambulation. Therefore, the robotic devices usually result in unnatural ambulation and may even cause significant discomfort to the wearer.
As such, many commercially available knee orthoses remain passive and non-adaptive to the wearer even today. These devices typically stabilize the knee joint medial-laterally, and limit the extent of knee flexion and extension. As such, they do not provide power or significant assistance to the user in walking, getting out of a chair, and ascending slopes and stairs, etc.
In level-ground walking, a healthy biological knee generally behaves like a spring during early to mid-stance, where knee torque is proportional to knee angular position. Further, during slope descent, the biological knee generally behaves like a variable damper, dissipating mechanical energy as heat to lower the body's center of mass with each step. Still further, during slope ascent, the biological knee behaves like a torque source, applying a non-conservative propulsive torque throughout early to mid-stance to lift the body's center of mass upwards with each step.
Some common major complications of knee extensor weakness are an inability to apply: 1) damping control during slope/stair descent, 2) spring stiffness control during early to mid-stance in level-ground walking, and 3) non-conservative propulsive torque control for slope/stair ascent and sit-to-stand maneuvers. Due to these various complications, a patient with knee extensor weakness frequently experiences a decrease in self-selected walking speed for level-ground and slope/stair ground surfaces, as well as an increase in walking metabolism while traversing these ground surfaces. Therefore, there is a need for improved systems and methods of permanent assistive devices for the treatment of lower-extremity pathology.